Glass ceramics with a lithium silicate crystal phase and the use thereof in dental products are known from the state of the art. For example, PP 1 505 041 describes lithium silicate glass ceramics which, in the form of lithium metasilicate glass ceramics, are processed by means of CAD/CAM processes to form the desired dental restorations, wherein a subsequent heat treatment leads to the conversion of the lithium metasilicate (Li2SiO3) phase into lithium disilicate (Li2Si2O5) phase and thus to the formation of high-strength lithium disilicate glass ceramic. Machining of the glass ceramic after the formation of the lithium disilicate phase is, in particular because of the high strength thereof, time-consuming and associated with high tool wear.
Glass ceramics which contain wollastonite as crystal phase are also known.
Wollastonite glass ceramics are primarily used as façade materials in the construction industry (cf. Höland, Beall, “Glass-Ceramic Technology”, Wiley, USA, 2nd Edition, 2012, pp. 114-116).
DD 247 574 describes glass ceramics with apatite and wollastonite as crystal phases. The glass ceramics are used for bone replacement and their high bioactivity means that they can form a firm bond to the bone in the living organism.
DD 262 366 discloses restorative tooth materials made of glass ceramics, which contain apatite and moreover wollastonite, as well as optionally perovskite, cristobalite and/or sphene as crystal phases.
DE 692 04 791 describes glass ceramics, which are used to produce tableware. The glass ceramics comprise, as predominant crystal phase, lithium disilicate, as well as small proportions of spodumene, cristobalite and wollastonite.
US 2005/0079226 describes bioactive glasses, which are used as sintering aid in materials for replacing bone. After crystallization, the glasses comprise wollastonite and diopside as crystal phases.
Bioactive ceramics are known from U.S. Pat. No. 5,356,436, which serve to replace bones and which, on contact with body fluids, can form for example hydroxyapatite on their surface. The ceramics can have e.g. diopside, wollastonite, alite, belite, akermanite, monticellite, forsterite, protoenstatite and tridymite as crystal phases.
U.S. Pat. No. 5,711,763 describes bioactive implants made of a metallic substrate, in the surface of which ceramic particles are embedded. The ceramic materials can originate for example from the group consisting of diopside, wollastonite, alite, belite, akermanite, monticellite, forsterite, protoenstatite and tridymite.
However, the known glass ceramics have a number of disadvantages. With these, in many cases the translucence cannot be adjusted over a broad range as is desirable for dental materials which can be used for many purposes. Moreover, with these, simple machining is often not possible. In addition, their strength often proves not to be sufficient to allow them to be used as restorative dental material.